4.1 Key Findings
The LM-35 temperature sensor gives a reading of around 33ºC to 34ºC that is very similar to the reading from the TMP-36 sensor. The chart (Fig. 3.1) shows that the two graphs are mostly overlapping each other, indicating that both sensors are functioning properly.
Temperature Control System Testing
Test I is set in an air-conditioned laboratory set at 25ºC. The temperature sensor after being calibrated correctly, showed a temperature reading of 26ºC to 28ºC. The data roughly correlates to the air-conditioned room temperature of 25ºC, indicating that the values are correct. However, there is an observable 1-2ºC difference in the temperature readings and the preset room temperature. When the threshold temperature of 27ºC is reached, the relay switches on immediately, powering the DC motor. The relay switches off when the temperature reading is less than 27ºC, thus proving that it worked.
Test II is in the open-air setting. The temperature sensor after being calibrated correctly, showed a temperature reading of 28ºC to 31ºC. Since the temperature in Singapore is usually 27ºC to 32ºC, the temperature sensor’s reading is acceptable as it is within 1-2ºC from the typical weather temperature range. The threshold temperature of 27ºC is met, and thus the relay remains activated throughout the one-minute duration of the test, and the DC motor is continuously powered.
4.2 Explanation of Key Findings
This shows that the sensors are working and LM-35 is working correctly. It means that the results are also spot on and accurate.
Temperature Control System Test I & Test II
Since Test I had been conducted in cooler temperatures, the temperature range would be from 25ºC to 26ºC so the sensor should be showing values near. However, there is an observable difference of 1-2ºC which is probably caused by the current flowing through the circuit, causing the temperature reading to increase by 1-2ºC. The relay was able to switch on and off when the temperature exceeded or went below 27ºC respectively because of the accurate connection between the relay and Arduino Uno.
Since Test ll was conducted in open air, the temperature range should be from 26ºC to 31ºC, thus the sensor should be showing values near. However, there is an observable difference of 1-2ºC which is probably caused by external factors such as the wind or the current flowing through the circuit. The relay was able to switch on and off when the temperature exceeded or went below 27ºC respectively due to the accurate connection between the relay and Arduino Uno.
4.3 Evaluation of Engineering Goals
Our goal of constructing a temperature control system was met, with the entire system excluding the aquarium chiller working.
4.4 Areas for Improvement
- We could also get a new and accurate temperature sensor which is waterproof. Preferably a new LM-35 or a TMP-36 sensor.
- We could also get a chiller instead of the motor we are using to control the temperature.
- We need to get an electricity meter so as to compute the amount of electricity used up by the chiller, in the unit of watts and send them to the Arduino. This is needed so as to see how much difference in terms of energy-efficiency a relay system that switches on the cooling mechanism when required, compares to a chiller that is constantly switched on permanently.